Transmission of Rabies by Bats in South America

By Jonathon Marioneaux

Halloween is still weeks away but it is never too early to get into the spirit of ghosts, goblins, and vampires.

Two common Halloween characters are the vampire and the bat so it is fitting to review vampire bats and their real impact on modern society.  In addition, another favorite of Hollywood is the zombie, depicted as a flesh eating undead corpse infected by a rapidly progressing virus.  The closest virus that causes these symptoms is the rabies virus which makes its host bite other animals in order to spread the virus by contaminated saliva. In my research of these two organisms (vampire bats and rabies), I discovered an interesting mini-literature review published in 2003 on the spread of rabies by vampire bats in South America.

Vampire bats are the principle spreader of rabies in South America. The virus infecting humans and livestock causes millions of dollars’ worth of damage to local economies. These bats are known as haematophagous bats belonging to the order Chiroptera with the most well-known species being the hairy-legged vampire bat (Diphyella ecaudata) and the rarer Desmodus rotundus. These bats feed on animals ranging from snakes to amphibians and cattle to humans and drink between 15 and 25 milliliters of blood per meal.  During their blood meal the bats spread the rabies virus through their saliva resulting in paralytic rabies.  Rabies has an incubation period of 21-150 days and causes muscular tremors, excessive salivation, spasms, and erratic activity.  If left untreated rabies is almost 100% fatal with only three known causes of survival without prophylactic treatment at the time of publication. Rabies can be prevented by the rabies vaccine however it is only given irregularly in South American livestock thus leaving many animals susceptible to paralytic rabies.

In South America, rabies has been blamed for expanding bat populations. Different population control methods have included lethal gas and/or dynamiting bat caves and coumarin paste. These methods led to the death of enormous quantities of bats but only a slight reduction in the numbers of rabies cases.  The rabies virus is spread by saliva and asymptomatic bats do not excrete infectious virions therefore the majority of the bats killed probably did not have rabies.  The spread of rabies in humans is mainly in areas that were previously covered by rain forests that were cleared to make build ranches and urban areas.  The main site of transmission is usually in the toes of individuals living in hazardous housing.

Therefore, urban sprawl and deforestation have led to the spread of rabies from bat populations to humans and livestock.  The current methods of controlling rabies, such as dynamiting caves and gassing known populations, may have the unintended effect of killing beneficial bats such as insectivorous (those that feed on insects) and nectarivorous (those that feed on nectar).  A more effective way of reducing the damage to livestock is more consistent animal vaccination practice which is effectively makes the animals vampire bat repellent.  In addition, educational campaigns should be introduced to reduce the “Dracula” image that many bats have.  It is widely known that bats are beneficial to the ecosystem and must be protected. Indiscriminate killing of bats might make a good Hollywood thriller but it is not good for the environmen

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